Systematics Section / ASPT
Tank, David , Olmstead, Richard .
Geographic disjunction or morphological convergence? The evolutionary origin of a second radiation of annual Castilleja species in South America (subtribe Castillejinae: Orobanchaceae).
Phylogenetic analyses of chloroplast (cp) and nuclear ribosomal (r) DNA sequence data has shown that the mostly perennial genus Castilleja has evolved from a grade of annual Castilleja species distributed chiefly in California. In addition to the North American annual species, a second geographic center of annual Castilleja species is in South America with seven annual species distributed in Chile and Andean Peru. The South American annuals are similar in both vegetative and reproductive morphology to those in North America, and are traditionally classified with the North American annual species in section Oncorhynchus. Based on previous morphological and cytological studies, it has been hypothesized that some of the six Peruvian annuals are allopolyploids involving hybridization of annual and perennial South American Castilleja species. Alternatively, this second radiation of annual species in South America may be derived from widely disjunct annual ancestors distributed in North America. Phylogenetic analyses of cpDNA, nuclear rDNA, and low-copy nuclear gene sequences have allowed us to test these competing hypotheses and determine whether the South American annual species are derived from disjunct annual ancestors, or are the result of in situ evolution, perhaps involving allopolyploidy, resulting in the same the same overall morphology.
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1 - University of Washington, Department of Biology, Box 355325, Seattle, Washington, 98195-5325, USA
low-copy nuclear genes
Presentation Type: Oral Paper
Date: Tuesday, August 16th, 2005
Time: 11:15 AM